For more than a week, Ethiopian government forces have been fighting against a powerful regional government in the country's north and hundreds are reported to have died.
Prime Minister Abiy Ahmed, a Nobel Peace laureate, ordered the government offensive after accusing the rival Tigray People's Liberation Front of launching an attack against Ethiopia's military last week.
Thousands of people have been displaced, as government planes bomb targets in the Tigray region. The rhetoric is hardening on both sides of the conflict, raising fears it could escalate into a full-out civil war and destabilize an already fragile region.
In a nightmare scenario, the conflict could pull in neighboring countries, including Sudan, which is working through a delicate transition of if its own, and Somalia, which is still fighting an Islamist insurgency.
Here are some key points to understand:
How did this conflict start?
It has deep roots. But essentially, it's a power struggle that goes back to 2018, when a popular uprising brought Abiy to power.
He ushered in democratic reforms and negotiated an end to what had become a cold war with neighboring Eritrea. But he also dismantled Ethiopia's ruling party, the Ethiopian People's Revolutionary Democratic Front, which had run the country for almost 30 years.
The EPRDF, which appointed Abiy, was a coalition of ethnically based political parties. The Tigray People's Liberation Front dominated the coalition and had amassed a lot of power as an ethnic minority. Tigrayans make up about 6% of Ethiopia's population.
When Abiy sidelined them, TPLF leaders retreated to their home region in northern Ethiopia. Since then, Abiy has accused them of trying to destabilize the country. In a briefing document sent to journalists on Thursday, his office directly accused the TPLF of orchestrating ethnic violence across the country.
"Hidden hands of the TPLF were there in the killings of civilians in many different parts of the country," the document read.
It cited intelligence, but didn't provide evidence. The TPLF has in the past denied similar accusations.
Regardless, that violence has displaced more than 3 million people over the past two years, according to the Internal Displacement Monitoring Centre.
But things worsened dramatically once COVID-19 hit Ethiopia, the African continent's second-largest country by population. Abiy was supposed to guide the country through its first truly democratic elections this summer. But citing the pandemic, he postponed them.
The TPLF argued that amounted to an unconstitutional extension of the federal government's term. So they defied Abiy's orders, created their own electoral commission and held their own regional elections. The federal government declared the Tigray elections unconstitutional and both sides began trading accusations of illegitimacy.
Abiy said the TPLF crossed a red line last week, when it allegedly organized a multi-pronged attack on the Ethiopian military's Northern Command — a "treason that will never be forgotten," Abiy said.
The TPLF denied the attack. On its television station, after the fighting broke out, the region's president, Debretsion Gebremichael, called for dialogue. In a letter to the African Union, he accused the government of a power grab, and accused Abiy of imprisoning his opponents and trying to turn Ethiopia's ethnic federalism into a system where the prime minister holds all the power.
"Dr. Abiy Ahmed's one-man dictatorial regime has started to unravel the constitutionally-established state institutions," he wrote. "He is also endangering the unity of this ancient country."
How serious is the fighting?
The internet and phone lines have been shut off in the conflict zone, so it has been a hard story to report. But things look grim. The Ethiopian military has said its forces have killed some 550 fighters.
Redwan Hussein, a spokesman for Ethiopia's State of Emergency Task Force, told a news conference he doesn't have exact numbers of casualties because forces are still trading fire. He says the communications blackout, for which he blames the TPLF, has affected even the government. So, he says, when the government takes control of territory, they will collect bodies and count.
On Thursday, Amnesty International said scores — likely hundreds — of apparent civilians were killed in a town at the western edge of the conflict. Amnesty said it hasn't been able to confirm who was responsible for the killings, that but witnesses told the group that TPLF-affiliated militias attacked with machetes, axes and knives. NPR has been unable to reach TPLF officials for comment.
The government is also bombing targets across the Tigray region and the United Nations' refugee agency says that some 7,000 Ethiopians fleeing the fighting have crossed the border into Sudan. The U.N. says that even before this conflict started, there were already about 96,000 Eritrean refugees and another 100,000 people who had been internally displaced in this part of Ethiopia.
"Roads are blocked and electricity, phone and internet are down, making communication nearly impossible," the agency said in its statement. "There is a shortage of fuel, and banking services have halted resulting in a lack of cash."
Will the situation worsen?
This conflict has the potential to be devastating. Some scholars have warned Ethiopia could break apart in the way Yugoslavia did in the 1990s.
The government has downplayed the fighting, calling it a "law enforcement operation."
Kiya Tsegaye, an Ethiopian political analyst, says the government has alienated the TPLF from its neighbors. Abiy has made deals with Eritrea and the new government of Sudan, leaving the TPLF with few ways to receive the weapons it would need to keep fighting.
But he says the TPLF is no ordinary militia.
"They have dominated the security and the military for almost three decades, and they have all the information and the top secrets of this country," he says. "They know the Achilles' heel."
The government alleges that when TPLF fighters attacked their troops last week, they also stole missiles that may be able to reach the capital Addis Ababa.
Another worry: an unstable Ethiopia could destabilize the region and perhaps even other parts of the country, which were already on edge.
One African diplomat, who follows Ethiopia closely and spoke on condition of anonymity to be able to speak candidly, says the warnings of a explosive conflict had existed for a while.
Just as Abiy came to power, a grenade was thrown his way at a public rally, and in late 2018, his own soldiers marched into his palace in an attempted coup. Everyone knew, the diplomat says, that this brew of ethnic states within Ethiopia, a government struggling with legitimacy and decades of built-up grievances could someday explode into war.
"Nobody seems surprised," the diplomat tells NPR. "But nobody seems to know what to do."
Are there any signs that the two sides can come together?
Not at the moment. The African Union has called for an immediate ceasefire. But Abiy has made it clear he will not negotiate until TPLF leaders are in custody and the cache of weapons held by the regional government is destroyed.
Abiy won the Nobel Peace Prize. And now he is presiding over a brewing war?
It's surprising. When he came to power, taxis and buses across Ethiopia plastered pictures of Abiy right next to those of Jesus. People on the streets said he had been sent by God.
Abiy was awarded the Nobel Peace Prize last year for his democratic reforms and for officially ending Ethiopia's war with Eritrea. In his acceptance speech, he railed against war. He himself fought in the Ethiopia-Eritrea war in the late 1990s, a war he described as the "epitome of hell."
"I've seen brothers slaughtering brothers on the battlefield," he said. "I have seen older men, women and children trembling in terror under the deadly shower of bullets and artillery shells. War makes for bitter men, heartless and savage men."
Now, just a year later, his jets are dropping bombs in some of the same places that war was waged.
Abiy, says Hussein, the government spokesman, is faced with a threat to the "very existence of the nation."
"The only thing he has to do is to defend it," he says. "So if there is a second Nobel Peace Prize, then he has to win it again, because he is still salvaging his country. He is still bringing hope to Ethiopians and defeating some terrorist gang leaders."